It is well known to apply compositions of trace elements such as boron to a crop or a crop area in which a crop is being grown or is to be grown. The farmer often prefers to apply such materials to the crop or crop area by spraying on an aqueous solution, and so it is desirable to be able to supply the farmer with a concentrate that can readily be dissolved or dispersed in water using simple mixing machinery.
Boron is generally applied to a crop in the form of a borate, usually sodium borate or sodium polyborate. It is difficult to dissolve commercial solid sodium borate or polyborate in a large volume of water using simple apparatus, and so it is desirable to supply aqueous concentrates. Unfortunately the maximum concentration of active compound in these concentrates is always very low. Thus the maximum concentration of sodium borate in water that can be obtained is about 0.5%, calculated as boron. The maximum concentration of sodium polyborate approaches 2%, measured as boron. By including other components, supersaturated solutions containing up to 3% measured as boron can be obtained (these and other percentages herein are by weight).
It is known to disperse sodium borate or polyborate in an organic liquid in which it is insoluble and which includes emulsifying agent, so that when the resultant concentrate is mixed with water, the borate compound dissolves and the oil emulsifies. In practice, however, the product is viscous, quite difficult to mix into a large bulk of water, and gives a cloudy emulsion, rather than the desired clear solution. More importantly, the product is unstable and tends to settle out, producing a very hard precipitate which is very difficult to re-mix into the product or into water.